Folks,
Very interesting discussion, particularly the latter twist.
Yes, if one has the luxury of avoiding circling approaches, take the option.
However, maintaining MDA until established on finals is often creating a greater potential risk than it may be intended to avoid. For PANS-OPS players, the protected airspace is fairly large and you may well be able to use the airspace to your advantage in achieving a reasonable finals profile from MDA - provided you have and maintain adequate visibility. For TERPS players, the protected airspace is ridiculously small (compare Cat C PANS-OPS at 4.2nm with CAT C TERPS at 1.7nm!!) and rolling out on high final (or was that high high high final) may well invite the unstabilised death dive that seems to cause more accidents then flying into the ground while descending around base.
Yes, there are some difficulties in getting adequate data for procedure design but PANS-OPS does include factors for many of the issues that JT raises. We should generally remember that aircraft operate into these places by day and as part of their normal circuit operations will invariably identify obstacle issues and, more variably, report problems to the procedure designers. Thus, even if a procedure is not flight tested, you are not totally committing to the unknown.
Furthermore, ICAO requires route and aerodrome qualification for scheduled operations - specifically so that you are not taking a sh*tload of passengers on a voyage of discovery during a circling approach at night. Charter operators face a more difficult problem, but not an insurmountable problem if one is prepared to invest the time and resources.
So, how do I manage the risk of descending at the appropriate point on the cicrling flight path? I work out where I should be at my OCH on finals (for me +400ft) and then I work back up and around the base turn to plan some gates (let's say +800ft mid base and +1200ft commencing the turn). If I commence the base turn abeam my finals roll-out point, then I should be about 1.2nm past abeam the threshold. Note that under TERPS that is as far as I can afford to go before turning!! Now I look at the circling minima and work out what I have to do to intercept that flight path.
As much as I hate them, it is the planning, practice and pucker factor that drives the discipline to get them right. But there is a big difference between respect and fear - find a way to get rid of the latter in favour of the former. And until we have straight-in approaches everywhere, circling is still going to exist and will still need to be approached professionally.
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Stay Alive,
[email protected]
[This message has been edited by 4dogs (edited 29 June 2001).]